function Log(target: Function, key: string, parameterIndex: number) {
	let paramName = key || target.prototype.constructor.name;
	console.log(target);//指向类 Car
	console.log(key);//指向函数名 add
	console.log(parameterIndex);//第几个参数,从0开始,值为:1
}

class Car {
	nameA: string;
	constructor() {
	}
	add (val1: string, @Log val2: string) {
		this.nameA = val1 + val2; 
	}
}
